JPH03204299A - Acoustic equipment - Google Patents

Abstract

PURPOSE:To drive an acoustic equipment with a usual power amplifier by driving a speaker with a difference between the entire drive signal and component signals other than that at a specific frequency band, that is, with a component signal at the specific frequency band in the drive signal. CONSTITUTION:The entire drive signal drives one input terminal (with respect to a ground terminal) of a speaker 2 and a component signal at frequency bands other than a specific frequency band in the drive signal drives the other input terminal (with respect to a ground terminal) of the speaker 2. That is, a usual power amplifier 1 is used as a drive signal source and the speaker 2 is differentially driven through a path from the usual power amplifier 1 and a path (auxiliary path) of an auxiliary amplifier 31 branched from the path of the amplifier 1 and the auxiliary path is used to set the drive characteristic. Thus, the band of the drive signal source such as that of the power amplifier is not limited especially except that the band includes all or a part of the specific frequency band and the user uses freely a preferred power amplifier to drive the speaker.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an audio device configured such that a specific frequency band component signal of a drive signal is supplied to a speaker, and particularly relates to a passive dividing network. The present invention relates to an audio device that is constructed without using a conventional passive dividing network and driven by a normal power amplifier in the same way as that using a conventional passive dividing network.

[Prior Art] Conventionally, dividing network methods and multi-amplifier methods have been known as methods for driving multi-way speaker systems.

However, the dividing network method
A large-capacity LC actual element is required, and as a result, the sound is distorted due to the magnetostriction of the inductance element (especially,
Cutoff frequency f of filters composing the network
(Conspicuous when C is lowered) ■In order to reduce the magnetostriction, the core of the inductance element must be made larger, so the element becomes larger.■The resistance of the winding of the inductance element increases the resistance of the speaker and drive system. The DC resistance increases, the Q of the speaker increases, and the braking becomes ineffective. Also, the capacitor needs to be non-polar (bipolar) and large capacity for AC, and generally has a low tan δ and the accuracy of the capacitance value. (that is, the accuracy of dividing) is also low.

■Since the load is not a pure resistance but a speaker whose impedance changes depending on the frequency, it is difficult to design network characteristics.■Also, if an attenuator is installed to adjust the frequency characteristics of the output sound pressure, damping etc. There were problems such as further adverse effects on the characteristics of

On the other hand, the multi-amplifier method solves the problems of the dividing network method, but
The entire system, including channel dividers and power amplifiers for each band, must be handled as a whole, especially for systems where the speaker system and amplifier can be selected arbitrarily, i.e., where the user can drive the speaker system with the amplifier of their choice. Another problem was that it could not be used as a speaker system.

[Problems to be Solved by the Invention] This invention was made in view of the problems in the conventional example described above, and it solves the problem of the multi-way speaker system.
An object of the present invention is to provide an audio device that can be constructed without using an LC real element (passive) day-hiding network and can be driven by a normal power amplifier like a conventional passive dividing network system.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, in an acoustic device configured such that a specific frequency band component signal of a drive signal is supplied to a speaker, the entire drive signal is supplied to a speaker. One input end of the speaker (between the ground end) is driven, and the other input end of the speaker (between the ground end) is driven by a component signal other than the specific frequency band of the drive signal. It is configured to be driven.

As a specific example, a normal power amplifier is used as the drive signal source, and a speaker is differentially driven by a path from the normal power amplifier and an auxiliary amplifier path (auxiliary path) branching from this path, and the auxiliary amplifier is Set the drive characteristics using the route.

[Operation] According to the configuration, the speaker is driven by the difference between the entire drive signal and the component signal outside the specific frequency band, that is, the component signal in the specific frequency band of the drive signal.

[Effects] Therefore, the acoustic device of the present invention is not particularly limited except that the band of the driving signal source, for example, a power amplifier, includes all or a part of the specific frequency band, and the user can freely set the frequency band to the user's preference. It can be driven using an amplifier.

Furthermore, since the auxiliary amplifier operates in cooperation with a driving amplifier, such as a normal power amplifier, it generally requires a relatively low capacity and small size, such as a small IC. This advantage is particularly important when the transfer characteristic T(s) of the auxiliary path is T(s)>O
This is noticeable when the output of the auxiliary amplifier has the same polarity as the output of the driving amplifier.

[Example] Hereinafter, the present invention will be described in detail using the drawings. In addition,
In each figure, common or corresponding parts are represented by the same reference numerals.

FIG. 1 shows the basic configuration of an audio device according to an embodiment of the present invention. This audio device consists of a pair of connections 411 . Drive signal V supplied via I2
A pair of input terminals Sl with a specific frequency band component signal of i
, S2.

One input end S1 of the speaker 2 is connected to one of the connection ends 11, and the other connection end I2 is connected to the operating reference potential (ground) ME of the auxiliary amplifier circuit 3. Further, the auxiliary amplifier circuit 3 has an input end connected to the one connection end 11, and an output end connected to the other input end S2 of the speaker 2.

The auxiliary amplifier circuit 3 has a transfer gain frequency characteristic T(s) corresponding to the specific frequency band, and generates an output vO with respect to the human input signal vi such that Vo=V i −T (s).

The speaker 2 is supplied with the drive signal Vt at one input terminal S1, and the output Vo=vi-T(s) of the auxiliary amplifier circuit 3 at the other input terminal S2. Therefore, the speaker 2 is driven by the signal VL as follows: VL=Vi-Vo=Vi [1-T (s)]. From this formula, the first
In the device shown in the figure, the speaker drive characteristic that is the target for driving the speaker 2, that is, the drive signal source connection terminal If
, I2 to the input terminals S1 and S2 of the speaker 2, the transfer characteristic G(s) is G(s)=1-T(s).

FIGS. 2A and 2B show examples of auxiliary amplifier circuits having such transfer characteristics. The auxiliary amplifier circuit 3 in FIG. 2A includes a speaker driving auxiliary amplifier 31 with a gain of 1, and an auxiliary amplifier 3
1, and a transfer characteristic imparting circuit 32 connected in series to one input. The transfer characteristic of the transfer characteristic imparting circuit 32 is T
(s). The auxiliary amplifier circuit 3 of FIG. 2B is the same as that of FIG. 2A, with a voltage feedback amplifier 33 added thereto. This voltage feedback amplifier 33 is used as a DC servo amplifier by configuring the inverting input side as an integrating circuit, for example.

Generally, when T (s) has a characteristic of second order or higher, transfer gain frequency characteristic G (s) = 1 - T (
s) is difficult to produce directly. For example, T(s
) is a second-order high-frequency cutoff characteristic as shown in Figure 3A, the characteristic G(s) is! As shown in Figure 3B, it changes in a complicated manner. In such a case, the transfer characteristic imparting circuit 32 may realize the characteristics T(s) and G(s) as an active type. In the case of an active type, the auxiliary amplifier 31 or the feedback amplifier may also be used as the active element. Further, even if the T(s) is a first-order characteristic, it is possible to provide the transfer characteristic imparting circuit 32 in the feedback system of the auxiliary amplifier 31.

Next, an explanation will be given of the operation of the acoustic device shown in FIG. 1 when the transfer gain frequency characteristic T(s) of the auxiliary amplifier circuit 3 is set to the band attenuation (band elimination) characteristic as shown in FIG. 4.

In FIG. 1, between the drive signal source connection terminal If-I, that is, the speaker input terminal Sl and the ground terminal E, as shown in FIG.
A low frequency component element 1 as shown in and a component within the attenuation band (
When a signal containing a midrange component (I2) is applied, the auxiliary amplifier circuit 3 amplifies only the signal component element 1 within the passband with a gain of 1, and outputs the amplified signal.

Therefore, between the speaker input terminal S2 and the ground terminal E, a signal consisting only of the low frequency component element 1 as shown in FIG. As a result, between both input terminals 5l and S2 of the speaker 2,
A signal obtained by subtracting the signal shown in FIG. 5A from the signal shown in FIG. 5A, that is, a component signal consisting only of the mid-range component element 2 as shown in FIG. 5C is applied. Figure 6A
-C indicates the transfer gain frequency characteristic G(s) or T(s) of each part corresponding to the waveforms of FIGS. 5A to 5C, respectively.

In this way, in the device shown in FIG. 1, the auxiliary amplifier circuit 3
By appropriately setting the attenuation band of the auxiliary amplifier circuit 3, the speaker 2 can be driven only with component signals in a desired frequency band of the drive signal. I can do it.

In addition, the auxiliary amplifier circuit 3 has a small transfer gain in a band where the drive current of the speaker 2 (that is, the output current of the auxiliary amplifier circuit 3) is large, so the output voltage is attenuated and has a small amplitude, and conversely, the pressure voltage has a large amplitude. The driving current of the speaker 2 becomes small in the pass band where Therefore, this auxiliary amplifier circuit 3
A device with relatively low power consumption, relatively low capacity, and small size is sufficient.

FIG. 7 shows an embodiment in which the present invention is applied to a three-way speaker system.

In the figure, the auxiliary amplifier circuit 3a outputs the drive signal Vi supplied to the drive signal source connection terminal If, I2 to the woofer 2.
A bypass filter (HPF) having a transfer characteristic T(s)w as shown in FIG. 8A, in which the drive signal band a is an attenuation band and the other drive signal bands are passbands with a gain of 1.
It is. Further, the auxiliary amplifier circuits 3b and 3c each have an eighth circuit that has the driving signal bands of the squawker 2b and the tweeter 2c as an attenuation band, and the other signal bands as a pass band.
A band-eliminating filter (
BEF) and a low pass filter (LPF).

According to the configuration, as described above, each speaker 2 (
2a, 2b, 2c), the drive signal Vi is supplied with a transfer gain of Lx G (s) x= , =1-T (s) x1 (where x=w, s, t). That is, of the drive signal ■i, the woofer 2a receives a low-frequency component that is a component signal in a band that is not attenuated by the bypass filter 3a, and the squawker 2b receives a mid-frequency component that is a component signal in a band that is not attenuated by the band-elimination filter 3b. However, the high-frequency component, which is a component signal in a band that is not attenuated by the low-pass filter 3c, is band-divided and supplied to the tweeter 2C.

In addition, in the system of FIG. 7, the auxiliary amplifier circuit 3a
, 3b, and 3c were set to be 1 in the pass band, O in the attenuation band, and positive over the entire band, but depending on the efficiency of each speaker 2, etc. It may also be a value other than 1 and O.

It is also possible to provide a variable element such as a variable resistor (attenuator) at the input end or feedback loop of each auxiliary amplifier circuit 3a, 3b, 3c to make the transfer gain T(s) variable and adjust the frequency characteristics etc. It is possible. Furthermore, the transfer gain T(s
) may be set to be negative in the attenuation band (ie, speaker drive band). In this case, the auxiliary amplifier circuit 3 and the normal power amplifier that supplies the drive signal Vi cooperate to perform negative impedance driving as disclosed in Japanese Patent Application Laid-Open No. 1-229599, and the reproduction characteristics of the speaker 2 are can be improved compared to the case of so-called constant voltage drive similar to ordinary power amplifiers (January 1999).
See patent application dated February 26th [Sound device and drive device for constructing such a sound device”).

FIG. 9 shows an embodiment in which the present invention is applied to a speaker system with a resonance boat.

The system shown in the figure houses a speaker 2 and an auxiliary amplifier circuit 3, which is a feature of the present invention, in a cabinet 6 having a resonance tube port 61.

Further, a DC power supply circuit 7 for operating the auxiliary amplifier circuit 3 and a protection circuit 8 for protecting each part of the circuit from deterioration and destruction due to overload or abnormal operation are also built into the same cabinet 6. Further, the auxiliary amplifier circuit 3 is configured to drive the speaker 2 with negative impedance in cooperation with the power amplifier 1 which is a drive signal source.

In the figure, the auxiliary amplifier circuit 3 includes a drive amplifier 31, a transfer characteristic imparting circuit 32, a feedback circuit 34, and a speaker current detection resistor Rs.

In the transfer characteristic imparting circuit 32, the voltage dividing circuit 352 converts the drive signal vi into a voltage dividing ratio k (k=)R
Partial pressure is 1+R2. The equalizer circuit 36 applies a transfer characteristic T(s) to -Vi to the output of the voltage divider circuit 35.The buffer amplifier 37 amplifies the output with an equalizer circuit 361 and provides an inverting input via a coupling capacitor C1 and a resistor R3. The signal is supplied to the terminal and is amplified to generate an output k. That is, the transfer gain of this transfer characteristic imparting circuit 32 is k[T (S)-t].

The drive amplifier 31 has this transfer characteristic imparting circuit 32. Thereby, the transfer gain of the auxiliary amplifier circuit 3 becomes IT(s).

Then, convert this 1-T(s) into the desired speaker drive characteristic G
(s), it is possible to apply only a desired frequency band component signal of the drive signal Vi to the speaker 2.

In the system shown in FIG. 9, the current flowing through the speaker 2 is further detected by a speaker current detection resistor Rs connected in series with the power amplifier 1 and the speaker 2, and is passed through a feedback circuit 37 with a transfer gain β to the drive amplifier. It is applied to the non-inverting input terminal of 31. In this way, the current detection resistor Rs
The voltage across the terminals is multiplied by 3 to obtain the output [1-T(S)] ・V
By adding to i (positive feedback), the output impedance ZO of the auxiliary amplifier circuit 3 becomes Zo=Rs (1-Aβ). Since this output impedance ZO is β output 1 at a sufficiently low frequency, Aβ>>1, resulting in negative resistance.

As a result, in the low frequency range, JP-A-122959
Negative resistance driving as disclosed in No. 9 is performed, and the speaker 2 is extremely strongly driven and braked, improving reproduction characteristics, especially low frequency characteristics. Alternatively, the cabinet 6, and by extension the entire speaker system, can be made smaller without impairing the reproduction characteristics.

The protection circuit 8 includes a D that turns off the relay contact Ry when a DC current exceeding a predetermined value flows through the speaker.
CC Prochiku 93 function, overcurrent protection that turns off relay contact Ry when overcurrent flows through the speaker, relay contact Ry when the heat sink temperature exceeds a predetermined value
heat sink temperature protection that turns off the power, and power supply muting that turns on the relay contact Ry after a predetermined time delay when the power is turned on to prevent noise generation and deterioration or destruction of the circuit or speaker due to the transient response when the power is turned on. A known circuit having a known function can be used. Further, protection means such as a primary fuse or a transformer internal temperature fuse may be provided.

[Brief explanation of drawings]

1 is a circuit diagram showing the basic configuration of an audio device according to an embodiment of the present invention; FIGS. 2A and 2B are circuit diagrams showing the auxiliary amplifier circuit in FIG. 1 in more detail; Figure 3 A and B
are characteristic diagrams for explaining the relationship between the transfer characteristic T(s) of the transfer characteristic imparting circuit in FIG. 2A and the speaker drive characteristic G(s) obtained thereby, and FIG. A characteristic diagram showing an example of the transfer gain frequency characteristic given to the auxiliary amplifier circuit in the device shown in the figure, FIGS. 5A to 5C are voltage waveform diagrams of various parts in the device shown in FIG. 1, and FIGS. FIG. 7 is a circuit diagram of a three-way speaker system according to another embodiment of the present invention; FIG. 8A -C are diagrams representing the transfer gain frequency characteristics of each auxiliary amplifier circuit in the system of FIG. 7, and FIG. 9 is a circuit diagram of a speaker system with a resonant boat according to still another embodiment of the present invention. . 2.2a, 2b, 2c: Speakers 3.3a, 3b, 3c: Auxiliary amplifier circuit 31: Auxiliary amplifier 32: Transfer characteristic imparting circuit It, 12: Drive signal source connection terminal Sl , S2 Speaker input terminal R5: Speaker current detection resistor

Claims (2)

[Claims] (1) In an acoustic device configured such that a specific frequency band component signal of a drive signal is supplied to a speaker, one input terminal of the speaker is driven by the entire drive signal, and a signal of a specific frequency band component of the drive signal is supplied to a speaker. An acoustic device characterized in that the other input end of the speaker is driven by a component signal other than the specific frequency band. (2) a speaker having a pair of drive signal source connection ends, a pair of input ends, one of which is substantially directly connected to one of the drive signal source connection ends, and an output end to the other speaker input end; an auxiliary amplifier circuit whose potential end is connected to the other drive signal source connection end and which outputs a signal corresponding to a component other than a specific frequency band of the drive signal supplied between the pair of drive signal source connection ends; An acoustic device, characterized in that the speaker is driven by a component signal in the specific frequency band of the drive signal.